Stretch film is made by producing a thin polymer film by extrusion; the film so produced can then be stretched in order to modify its mechanical properties. Such films can be given “cling” properties by adding a tackifier to the polymer from which the stretch film is produced. In some cases, the tackifier-containing films are stretched before being wound onto a roll, and in other cases the films are wound onto the roll without any stretching, and the stretching is carried out when the film is being unwound and wrapped around its load (such as several boxes stacked on a pallet).
A significant problem associated with the traditional manufacture of stretch film having cling properties achieved by the addition of tackifier is that it has generally been considered necessary to “age” the thin polymer film, prior to stretching (whether by pre-stretching before rolling or during wrapping), in a temperature-controlled environment to allow the tackifier to “bloom”, that is, come to the surface of the thin polymer film. It has been believed that if the film is stretched prior to the tackifier blooming to the surface, for example where a web of the thin polymer film were passed to a stretching mechanism shortly after production, the cling properties of the film are usually lost.